The present invention is directed to a pressure sensitive adhesive useful in transdermal administration of pharmacologically active agents, in particular estrogen and/or progestin active agents.
The transdermal delivery of therapeutic agents has been the subject of intense research and development for over 20 years These efforts have resulted in the creation of several commercially successful products whose advantages over other dosage forms are well documented. The skin, however, is an exceptionally well designed barrier. As a result, only a relatively small number of drug molecules are suitable for transdermal delivery, including hormones such as estrogen and/or progestin.
It is known to administer steroidal hormones such as estrogen and/or progestin active agents by transdermal means to a patient. See, for example, U.S. Pat. Nos. 5,108,995; 5,223,261; 5,242,951; 5,422,119; 5,460,820; and WO 96/08229. It has been found that such active agents are susceptible to crystallization within the adhesive matrix over time. Such crystallization inhibits the ability of the transdermal device to deliver the active agent to the patient.
The prior art does not provide a transdermal pressure sensitive adhesive which both serves as a satisfactory matrix for the delivery of an estrogen and/or progestin active agent as well as inhibiting the crystallization of such active agent in order to enhance the long-term effectiveness of the delivery system.